This invention relates to a method of making a component of the type comprising a metallic shell closed at one end and an insert of a polymeric material located within the shell.
In many types of component such as a closure member for a container, the component comprises simply a metallic shell or a metallic shell formed with a relatively thin lining of a suitable material by a coating process, such as a metal/polymer laminate. For most purposes, such components are satisfactory. However, for some types of components particularly closure members for high quality containers such as perfume bottles, the closure member takes the form of a metallic shell and an insert of substantial thickness which is formed from a polymeric material and is located within the shell. Conventionally, the metallic shell and the insert are formed separately, adhesive is then applied to the shell and/or the insert and the insert is then placed in position in the shell. However, this method of making a closure member suffers from the disadvantage that it requires several manufacturing stages and is correspondingly expensive.
Whilst it is therefore desirable to form the insert by moulding it in situ within the shell, in a conventional moulding process it is difficult to maintain consistent sealing integrity of the shell within the mould, so as to prevent leakage of polymeric material during moulding beyond the end of the shell. It is also difficult to achieve satisfactory location of the insert in the shell after the polymeric material has cooled and undergone shrinkage. It may be desired to form relief features on the shell for decorative or other purposes, but to form such features as a separate operation on the shell prior to inserting it into the mould cavity would involve additional manipulative and manufacturing stages and may require angular orientation of the shell in relation to the mould cavity. It has been found that over a wide range of thicknesses of the shell material the polymer pressures which are conventionally used in injection-moulding may be employed to reform the shell outwardly into one or more recesses which are suitably provided in the mould cavity wall. Thus at the same time as the insert is being moulded the shell may be formed with one or more relief features (i.e. protuberances) which may serve both for decorative purposes and for mechanically locking the insert against substantial movement within the shell to prevent or reduce relative movement.